Re: Fwd: Generating valid Haskell code using the GHC API pretty printer

Thomas Schilling wrote:

Forgot to include the list.

---------- Forwarded message ---------- From: Thomas Schilling Date: 2009/7/22 Subject: Re: Generating valid Haskell code using the GHC API pretty printer To: Jan Schaumlöffel

The pretty printer never prints { .. } for a do expression. You can control which things are printed unqualified by setting the "PrintUnqualified" part properly. The most straightforward way is to use GHC.mkPrintUnqualifiedForModule which only prints things qualified that are not imported in the given module. See 'withPprStyle' and 'mkUserStyle' in Outputable.

That said, if you're trying to do source-to-source transformations you probably want to keep the original layout as much as possible. GHC's pretty-printer isn't designed for that. GHC's syntax tree has very accurate source locations, so you could start from there and build your own pretty printer.

I believe, Language.Haskell.Pretty can properly output haskell code (and the GHC API should be able to do so, too. Does the GHC API output tabs?) Below is a snippet for parsing and printing only. Cheers Christian import Language.Haskell.Pretty as HP import Language.Haskell.Syntax import Language.Haskell.Parser import System.Environment processFile :: String -> IO () processFile file = do src <- readFile file case parseModuleWithMode (ParseMode file) src of ParseOk hsMod -> putStrLn $ HP.prettyPrint hsMod ParseFailed loc err -> fail $ err ++ " in '" ++ file ++ "' line " ++ show (srcLine loc) main :: IO () main = do args <- getArgs mapM_ processFile args